Three-dimensional viewing is of major significance for many industrial control operations. Thus, such apparatuses are used for example for controlling solder locations on printed circuits. In contrast to normal stereo microscopes, the exit pupil is greatly enlarged so that the eye of the viewer does not have to be in a precisely defined position in order to be able to observe the iamge. With that arrangement, the viewer does not have to look into two separate eyepiece tubes for a prolonged period of time, as is the case with conventional stereo microscopes. That affords ergonomic advantages and also results in less rapid eye fatigue.